Alloy containing magnesium, silicon, and calcium



is introduced in the form of calcium cyanamide.

United States Patent 3 Claims. 0175-134 The invention relates to the preparation of an alloy containing silicon, magnesium, and calcium which alloy is useful as a prealloy or addition alloy in the production of cast iron in which the graphite shall be present in spheroidal form (nodular cast iron).

One of the inventors, jointly with Jiirgen Motz et al., has disclosed in Patent No. 2,837,422 the preparation, properties, useful ranges and advantages of such addition agents which contain magnesium, calcium and silicon in specific proportions.

We have now found that such addition agents have a particularly good and balanced effect when in their preparation substantially the entire amount of the calcium It appears that the etfect of such preparation method on the nodularizing properties of the addition alloy is the more prolonged the higher the NzCa ratio is which is produced therein by the use of the calcium cyanamide. We prefer, therefore, to use the so-called white calcium cyanamide which has an N content over 25% up to 32%.

The addition alloys are prepared by introducing ferrosilicon into molten magnesium in such an amount that the melt contains about 3 to 11' parts of silicon and 1 to 3 parts of iron for 3 parts of magnesium. The calcium cyanamide is then added to said melt in such an amount that an alloy of the following composition is obtained:

Percent Mg 17 to 40 Si 35 to 60 Ca 3 t0 6 N 0.8 to 2.5 Fe, balance to 100 In said alloy the calcium is bound partly to silicon, partly it is present as calcium cyanamide finely suspended in the alloy.

The following example illustrates the method of the invention.

'Example 3,177,072 Patented Apr. 6, 1965 homogenized, and then 28 parts of white calcium cyanamide (32%)'are introduced portionwise. The melt is again homogenized, and the finished alloy is tapped. The alloy has a Ca content of 4.4 percent and an N content of 1.24 percent.

If desired, rare earths may be added preferably after the FeSi addition has been completed, for the purpose to render harmless certain metallic impurities.

The considerably improved effect of the thus prepared addition alloy over similar alloys prepared from calcium is shown by the following comparative tests.

An iron melt as cast treated with a nitrogen-free Fe- Si-Mg-Ca prealloy containing 4.4% Ca practically ceased to produce spheroidal graphite 15 minutes after the addition of the prealloy; if the same iron melt was treated with a similar prealloy prepared from black calcium cyanamide and containing 4.6% Ca and 0.84% N, still about 50 percent of the graphite were precipitated as spheroidal graphite after 15 minutes. If, under otherwise similar conditions, a prealloy made from white calcium cyanamide and containing 4.5% Ca and 1.26% N was used as addition agent, there was obtained after 15 minutes still about 90 percent of the graphite in the spheroidal form.

The prolonged nodularizing action of the prealloys made from calcium cyanamide on the castings of cast iron is of great importance. We believe that the slowingup of the rate of decline of the magnesium eliect by the use of prealloys containing calcium cyanamide may be explained by their N content, and particularly by a high NtCa ratio, which would explain also the greater efiiciency of prealloys made from white calcium cyanamide, due to their higher N contents.

We claim:

1. An addition alloy consisting essentially of about 17 to 40 percent of magnesium, 35 to percent of silicon, the balance being iron, and in fine suspension therein calcium cyanamide in an amount corresponding to 3 to 6 percent of calcium and 0.8 to 2.5% of nitrogen.

2. The alloy as claimed in claim 1 wherein the proportion of magnesium to silicon to iron is about 3:3-l1z1-3.

3. The alloy as claimed in claim 1 wherein the calcium cyanamide is white calcium cyanamide having a N content of more than 25 percent.

References Cited in the file of this patent UNITED STATES PATENTS 2,255,016 Smith et 1. Sept. 2, 1941 2,747,990 Morrogh May 29, 1956 2,749,237 Jordan June 5, 1956 2,762,705 Spear et al. Sept. 11, 1956 2,837,422 Motz et a1 June 3, 1958 FOREIGN PATENTS 548,216 Great Britain Sept. 30, 1942 658,707 Great Britain Oct. 10, 1951 

1. AN ADDITION ALLOY CONSISTING ESSENTIALLY OF ABOUT 17 TO 40 PERCENT OF MAGNESIUM, 35 TO 60 PERCENT OF SILICON, THE BALANCE BEING IRON, AND IN FINE SUSPENSION THEREIN CALCIUM CYANAMIDE IN AN AMOUNT CORRESPONDING TO 3 TO 6 PERCENT OF CALCIUM AND 0.8 TO 2.5% OF NITROGEN. 